This invention relates to activators for use in a well borehole or subsea environment, and more particularly, to electrically powered activators for initiating mechanical motion such as in a hydraulic fluid pump.
In oilfield practice, and particularly in the practice of offshore well drilling and completions, it has become more usual than unusual to have multiple well completions in a single borehole. Multiple well completions may be made at different depth levels in a single well borehole or multiple well bore holes may be drilled offset from a single central well borehole with perforations and completions in each of the offset wells. When this is done, a central passageway through well packers or other well tools disposed in the borehole, such as valves, pumps, or the like is usually required or desired to permit passage of tubing to each of the wells and/or completion levels in a single well borehole. Thus, an annular shape about such a central passageway for well tools, pumps, packer activation mechanisms, etc. which provides a central unobstructed passage therethrough has become a desired geometrical shape. Such an annular or toroidal shape about a central passage is provided in a solenoid activator and in a hydraulic pump in the present invention.
Typically in the prior art, annular solenoid coils (i.e. fully annular) such as that disclosed in U.S. Pat. 4,579,177 have been proposed for borehole use. In this patent a fully annular solenoid coil is used to move an annular armature member (which is also fully annular and concentric therewith) against a spring bias in a well tool. By fully annular it is intended to mean that the solenoid coil being described has an overall toroidal shape which is not interrupted for the full 360 degrees of its circumference about a central passage therethrough. This is to distinguish the geometry of the present invention which employs an interrupted annular shape. By interrupted annular shape it is intended to mean that a non continuous toroidal member is described which has a gap, or is interrupted, in its circumference about a central passage therethrough. If the axis of revolution of the toroid is taken as the axial direction, then the interrupted annular shaped object has a segment which is capable of axial motion with respect to the other portion of its body.
In the interrupted annular solenoid activator of the present invention the best use of the available volume or space in the annular wall of a well tool, pipe or other tubular structure is made. Solenoids have been wound toroidally about an actuator core which is concentric with the wire coil. Solenoids constructed in this manner as described in the U.S. Patent above generally take the form of a cylindrical volume filled with, for example, an armature or an actuator rod and an external body or air, to form a return path for the magnetic field. In the present invention an interrupted annular shaped first member of iron (or other magnetic material) forms the core of a wire coil wrapped thereabout to form an interrupted annular shaped solenoid core. The interrupted segment in the annular shaped solenoid core is generally a curved wedge shaped section or member thereof. This wedge shaped (curved) segment is capable of axial movement. This member may be fabricated of a permanent magnetic material having a desired north or south polarity. In another embodiment of the invention, this member may be ferromagnetic and spring biased. The passage of electrical current (either AC or DC) through the wire coil wound about the interrupted annular shape solenoid core causes a magnetic field of either constant (in the case of DC) magnetic polarity or varying magnetic polarity in the case of AC current in the core. This magnetic field attracts or repels the wedge shaped section or segment and causes axial motion of this member as it is mounted in the apparatus to allow such axial motion. In the case of passage of DC current through the coil, the wedge shaped member is attracted and held in a fixed position until the current removed or reduced. A return spring or the like may be employed to then cause reciprocal axial motion to return the wedge shaped member to its starting position.
In the case of an AC current being passed through the wire coil and using a permanent magnetically polarized material for the wedge shaped segment, the magnetic polarity of the wedge shaped member being constant, it is alternately attracted and repelled by the polarity of the AC magnetic field induced in the interrupted annular shaped first member. In either case of AC or DC activation the reciprocal axial motion of the wedge shaped member may be utilized to activate motion or propel other moving parts or systems.
In one particular preferred embodiment the axial motion of the wedge shaped segment is used to power the piston of a hydraulic pump used to supply hydraulic fluid under pressure to other hydraulic mechanisms in a well tool system in the borehole. The interrupted annular solenoid segment in this embodiment moves the piston and compresses springs which, upon their release, force the piston in the opposite direction. Thus a reciprocating motion is imparted to the piston for moving the hydraulic fluid.
The invention may best be understood by reference to the following detailed description thereof when taken in conjunction with the appended drawings, in which: